IF aged male C57BL/6J mice (20–22 months) are subjected to a two-phase sequential repair protocol — Phase A: a senolytic priming course of dasatinib (5 mg/kg IP, 2×/week for 3 weeks) plus quercetin (50 mg/kg IP, 2×/week for 3 weeks) to deplete the SASP-generating senescent cell population from the myocardium, followed immediately by Phase B: chronic intraperitoneal co-administration of paromomycin:neomycin at a 2:1 molar ratio (each drug at 50 mg/kg/day, 5 days/week) for 12 weeks to inhibit the Meis1-Hoxb13 transcriptional complex —

THEN compared to aged vehicle controls and to aged mice receiving either intervention alone, the sequential combination group will demonstrate:

• ≥1.5-fold increase in cardiomyocyte mitotic index (Ki67⁺/Aurora-B⁺/Troponin-T⁺ co-staining) relative to vehicle,
• ≥10% absolute improvement in left ventricular ejection fraction (LVEF) by echocardiography at 12 weeks post-treatment initiation,
• ≥20% reduction in fibrotic area (Masson's trichrome quantification),
• with comparable renal (serum cystatin C, urinary KIM-1) and auditory (ABR threshold shifts <10 dB) safety profiles between young adult (3–4 month) and aged cohorts,

BECAUSE the following causal chain operates on already-accumulated structural and transcriptional damage in the aged myocardium:

1. Aged myocardium harbors a dense senescent cell burden that constitutes accumulated damage. Senescent cells in the aged heart secrete a pro-inflammatory, pro-fibrotic SASP milieu (IL-6, IL-1β, TGF-β, PAI-1) that actively suppresses neighboring cardiomyocyte cell cycle re-entry, promotes interstitial fibrosis, and creates a microenvironment refractory to proliferative stimuli — this is accumulated tissue damage, not future damage risk (Lewis-McDougall et al. referenced in Evidence Set Literature Output).

2. Senolytic pre-clearance (D+Q) removes this inhibitory damage layer. Dasatinib + quercetin selectively eliminates p16^INK4a^/p21^CIP1^-positive senescent cells via restoration of pro-apoptotic signaling. Their removal dismantles the SASP milieu, reduces local TGF-β signaling (which suppresses CDK2/CDK4 activity), and structurally softens the extracellular matrix, reconstituting a permissive microenvironment that young cardiac tissue presents constitutively.

3. Only after SASP clearance can Meis1-Hoxb13 inhibition function effectively in aged tissue. The paromomycin:neomycin (2:1) combination, validated in PMC11343477 as directly disrupting the Meis1-Hoxb13 protein–protein interface at the homeodomain interaction surface, releases cardiomyocytes from CDK inhibitor (p21, p16)-mediated cell cycle arrest (Identification of FDA-approved drugs that induce heart regeneration in mammals)[https://pmc.ncbi.nlm.nih.gov/articles/PMC11343477/]. In the un-primed aged heart, this signal is suppressed by SASP-driven CDK inhibitor re-induction; in the primed heart, the pharmacological block is the only remaining barrier.

4. **Released cardiomyocytes undergo sarcomere...

SENS category: GlycoSENS